Best Underground Water Storage Options ?

This assumes the tank will never fail. Is that a bad assumption ? Do these tanks ever fail when properly installed ?

chris florence wrote:First post here so be gentle on the "use the search function" comments ;) .

Side question - Is there any benefit that can be gained from these two large thermal masses as I design my RMH and off-grid power system

Kyle Neath wrote:

As a side-question, do you have any elevation change in your property? It seems like a bummer to have two tanks that both require pumps to operate.

We live on a steep slope so there's plenty of gravity to work with but digging a tank in above the grade of the house would be way more work than putting below grade. I'd have to build an access road to even get to a burial site. The tank in the house is already connected to a jet pump (1.5hp I think) to supply the house (with a pressure tank) but is plumbed in such a way that I can use the same pump to bring water in from an ouitside source to fill the tank as needed. Placing the tank below grade also simplifies the planned catchment system.

Rez Zircon wrote:What Kyle said. I don't like stuff I can't get at to maintain. Great way to ensure the part most difficult to get at is the one that fails!

And unless freezing is an issue with the existing tank, I wouldn't bury it at all. I'd put it above ground, on the highest point convenient to the house, and use its elevation as its own pressure system. (It's cheaper to pump occasional rainwater TO the tank than to run a pressure pump every day.) Build a barn around it and use the water mass as a heatsink, and the barn roof as your major catchment system -- a 1000 sqft barn could easily collect 500 gallons during a heavy rain.

What are you doing for filtering and purification? rainwater collected off any surface is going to contain a certain amount of poop from passing birds, and therefore coccidia (and increasingly, cryptosporidia which is much more pathogenic and difficult to treat).

Creighton Samuiels wrote:

chris florence wrote:First post here so be gentle on the "use the search function" comments ;) .

Side question - Is there any benefit that can be gained from these two large thermal masses as I design my RMH and off-grid power system

I've been thinking along the same lines myself, but a plastic tank might lose some of it's structural integrity if exposed to high temp water.  Considering the size of the tank you have, however, you might be able to raise the tank temp to 85 or 90 without significant problems.  It might even take more, but I wouldn't push it.

J. Jost wrote:Hi Chris,
We are in N. Idaho-- zone 5, and are considering installing an underground back- up water holding system also.
I second Kyle's post-
I have not heard of any plastic tanks failing, but, I would be leary of building a permanent structure over the tank.
Would you elaborate on the earthen roof, please?

chris florence wrote:
Freezing is definitely an issue where we live. It's what adds a lot of anxiety to thinking about a catchment system that doesn't depend on 500 feet of heat tape . We've ruled out an above ground tank at this point. We have about 3000sqft existing roof and will add another 1000 when we have the $ for the addition. We can catch over 4 times our current water budget based on annual rainfall for this area - (45,000 gal annually on the existing 3000ft) so don't really need any more roof...

Creighton Samuiels wrote:

chris florence wrote:
Freezing is definitely an issue where we live. It's what adds a lot of anxiety to thinking about a catchment system that doesn't depend on 500 feet of heat tape . We've ruled out an above ground tank at this point. We have about 3000sqft existing roof and will add another 1000 when we have the $ for the addition. We can catch over 4 times our current water budget based on annual rainfall for this area - (45,000 gal annually on the existing 3000ft) so don't really need any more roof...

HAve you considered a rainwater pillow?  This wouldn't take heat much at all, but nor would it require freeze protection.

http://www.rainwaterpillow.com/

EDIT: It wouldn't require *much* freeze protection, as the pump might need it.  If you use underground pex as your connection piping, you don't have to worry about freeze damage, but you could still end up with a freeze blockage at an inconvenient time.

chris florence wrote: Are you saying that it wouldn't require much freeze protection because I mentioned the possibility of thermal storage ?

I definitely wouldn't put one of those pillows outside, above ground in our zone but the option of putting it in the crawlspace sounds really appealing. It's about the same cost as an HDPE underground tank but there's no hole to dig. I have an extra tall crawlspace under the finished part of the house, which is also built with the ICF blocks. I'm assuming it probably never gets below freezing in there but I'll stick a hi-low thermometer down there and check it out this winter. If it will take any heat, that would be a great place to store it - kind of like a radiant heat bladder...

Creighton Samuiels wrote:

That exact idea occurred to me as I wrote the last post, and I sent an email to them asking how hot the water can be inside the pillow.

chris florence wrote:They don't mention anything about cleaning the "pillow" in the maintenance routine. I'm curious how one would deal with both sediments and biological contamination. Seems that a rigid tank is going to be easier to clean if necessary...

Creighton Samuiels wrote:But if you are using rainwater, there shouldn't be any sediment.

Rez Zircon wrote:

Creighton Samuiels wrote:But if you are using rainwater, there shouldn't be any sediment.

Not true -- depending on conditions, rainwater can have enough sediment that it looks like ditchwater. Rain catches dust in the air; your roof catches dust and sheds a certain amount of grit; trees shed organic particles even if you don't see obvious leaves etc. This area isn't even dusty and I've had to scrape mud out of the gutters -- washed down the roof by the rain. Sand and coarser particles aren't the problem, as they'll settle out easily enough; what clogs filters is suspended microgrit.

Creighton Samuiels wrote:

Rez Zircon wrote:

Creighton Samuiels wrote:But if you are using rainwater, there shouldn't be any sediment.

Not true -- depending on conditions, rainwater can have enough sediment that it looks like ditchwater. Rain catches dust in the air; your roof catches dust and sheds a certain amount of grit; trees shed organic particles even if you don't see obvious leaves etc. This area isn't even dusty and I've had to scrape mud out of the gutters -- washed down the roof by the rain. Sand and coarser particles aren't the problem, as they'll settle out easily enough; what clogs filters is suspended microgrit.

Well, sure.  If your roof is asphalt it could be bad. If your roof is metal, it's less likely.  Also, that is what the first flush devices are for; diverting the first couple gallons that come off the roof during a rainstorm.  That's where the vast majority of the dust & clutter will be anyway.  And there is supposed to be a high flow filter to catch the particulates on the way in.  So, there shouldn't be any sediment, but it could still be dealt with if necessary.

chris florence wrote:

Kyle Neath wrote:
As a side-question, do you have any elevation change in your property? It seems like a bummer to have two tanks that both require pumps to operate.

We live on a steep slope so there's plenty of gravity to work with but digging a tank in above the grade of the house would be way more work than putting below grade. I'd have to build an access road to even get to a burial site. The tank in the house is already connected to a jet pump (1.5hp I think) to supply the house (with a pressure tank) but is plumbed in such a way that I can use the same pump to bring water in from an outside source to fill the tank as needed. Placing the tank below grade also simplifies the planned catchment system.

chris florence wrote: I was hoping to pour a slab, or do an earthen floor on top of the tank and build an addition over the top of it (this assumes the tank will never fail. Is that a bad assumption ? Do these tanks ever fail when properly installed ?  

Corey Schmidt wrote:I have a few bits of info to offer, having done rainwater catchment systems for 5 different homes now.  
1:  it might be a good idea to shop around for the tank.  I recently purchased a 2500 gallon hdpe water tank (Norwesco) from Home Depot in Kenai Alaska for just over $1000.  
2:  an alternate means of collecting rainwater is to run the water from the gutter through a screen, first flush device, then into a 30-50 gallon barrel with a pump on a float switch that pumps it through filters into your tank, assuming you have electricity.  The first flush device can be in a conditioned space along with the catch and pump barrel (just be sure to put an overflow on the barrel as well as your big tank!). You can also put a diverter in your downspout to send all water away when everything is full (by manually turning a valve- easy if you switch from normal gutter to 2"dwv(drain/waste/vent) pipe (ABS). I usually pump sequentially through 30, 10, and 1 micron standard spun polyester filters 2" x10"-- filters should be available locally for under $7 each.  I usually have to change them 2-4 times per year, and the housings run around $30 each for culligan brand.
3.  starting for around $450 you can get a UV sterilizer.  If you put a 5 micron 4" x 20" filter after your pump then a UV sterilizer after that, you've got potable water throughout your house.  The UV sterilizer does need to operate continuously (i think its about 10 watts) and the bulb needs changed once a year (about $90).  Its recommended to do it this way rather than batch treatment before your tank because UV has no residual disinfecting power.
I did a write up on one system for a summer only cabin
https://permies.com/t/55399/potable-rainwater-harvesting-system-client
I hope some of this can be of benefit!  

John C Daley wrote:Here in Australia I use elevated tanks as my water source.
With no pumps, the tanks fill from shed roofs. My Hot water tank, with a thermo syphon solar panel system sits about 6 feet [1.8M] above the taps where it is used. I use 25mm or 1 Inch pipes to the taps and I have adequate water pressure for the domestic situations. The shower runs fine also.
When laying the pipes its important not to create an air pocket, because water will not flow through it. If I accidentally create an air pocket, I put a valve [tap ] at that location so the air can be let out. Sometimes an air valve can be used, but you may get a small discharge of water without realising it.

John C Daley wrote:I don't filter or purify the water, its ok for drinking  as it comes from the tanks.
I am surprised when I read of the things you do to water before using it.
Is it necessary?

John C Daley wrote:I don't filter or purify the water, its ok for drinking  as it comes from the tanks.
I am surprised when I read of the things you do to water before using it.
Is it necessary?

John C Daley wrote:Here in Australia I use elevated tanks as my water source.... I use 25mm or 1 Inch pipes to the taps and I have adequate water pressure for the domestic situations. The shower runs fine also.
....

Marcus vandell wrote: a cistern and as a foundation/slab, almost 17 years ago now and am pleased to say it's held up fantastically well. It measures 7m x 3.5m x 1.40m. So, that's some 34,000ltrs..

If you do decide to go concrete I'd be happy to go into details about how I built ours.